1. Field of the Invention
The present invention relates generally to a magnetic disk drive, and more particularly to a connection structure for supplying a write signal to a magnetic head or retrieving a signal read by the magnetic head from the magnetic disk drive to external equipment.
2. Description of the Related Art
In recent years, size reduction and thickness reduction have been advanced in a magnetic disk drive as a kind of external storage for a computer. Further, low power consumption in such a magnetic disk drive is also desired. In addition, an improvement in recording density of a magnetic disk is also demanded to obtain a large storage capacity, and the number of disks to be mounted in the disk drive is accordingly increasing.
In a magnetic disk drive for a computer, a contact start and stop (CSS) system defining the relation  relationship between a head and a disk is generally adopted. In this system, while the disk is being rotated at a high speed, a head flying force generated by an air flow due to high-speed rotation of the disk balances a pressing force of a suspension pressing the head on the disk, so that the head is kept at a microscopic flying height from the disk. When the rotation of the disk is stopped, the head is moved to a landing zone on the disk and comes to  into contact with the disk at this zone. In the rest condition of the disk, the head and the disk remain in contact with each other.
Conventionally, lead wires mounted on the suspension are used to supply a write signal to the head or take a signal read by the head out of the magnetic disk drive. However, as downsizing of the magnetic disk drive proceeds, the structure of the suspension to be adopted is being shifted from the above type that  in which the lead wires are mounted upon the suspension to another type that  in which a conductor pattern connected to the head is formed integrally on the surface of the suspension.
In a conventional magnetic disk drive adopting such a suspension with a conductor pattern, there is provided inside the magnetic disk drive a main flexible printed circuit sheet (which will be hereinafter referred to as a main FPC) for leading wiring to a printed circuit board provided outside the magnetic disk drive. Terminals provided at a base end portion of the suspension are connected through lead wires to terminals of the main FPC. The main FPC is fixed at its one end portion to an actuator arm by bonding or screwing. Accordingly, the lead wires are installed along a side surface of the actuator arm.
A magnetoresistive head (MR head) has been developed as a head in a recent magnetic disk drive. The MR head has an inductive element to be used in  for writing data and a magnetoresistive element (MR element) to be used in  for reading data. Accordingly, the number of signal lines is four in  when using the MR head as compared with a conventional general head requiring two signal lines. Such an increase in the number of signal lines causes an increase in the number of wiring steps where the number of steps is double that in the general head in connecting the terminals of the suspension through the lead wires to the terminals of the main FPC.
Further, since the number of the terminals is also increased, a double space for installing the terminals of the suspension and the terminals of the main FPC becomes necessary. However, in the recent magnetic disk drive designed to reduce its size and thickness, sufficient space for installation of the terminals is difficult to ensure. That is, the terminal installation space is small and the distance between the adjacent terminals must be reduced.
For these reasons, it is undesirable to use the  lead wires for the connection between the terminals of the suspension and the terminals of the main FPC. In this respect, there has been proposed a technique of connecting the terminals of the suspension and the terminals of the main FPC by using an interconnection flexible printed circuit sheet (which will be hereinafter referred to as an interconnection FPC). In this prior art, the interconnection FPC is attached to the side surface of the actuator arm to connect a conductor pattern formed on the suspension and a conductor pattern formed on the main FPC.
The advance of size reduction and thickness reduction of the recent magnetic disk drive as described above causes a reduction in thickness of the actuator arm. Further, the use of the MR head causes an increase in number of signal lines to be enclosed in the interconnection FPC. Accordingly, in the above prior art method where the interconnection FPC is attached to the side surface of the actuator arm, the width of the interconnection FPC is decreased with a decrease in thickness of the actuator arm to cause a problem such that it is difficult to ensure a necessary number of signal lines in the interconnection FPC and the pattern width of each signal line is reduced.
It is therefore an object of the present invention to provide a disk drive having a connection structure between a head and a main FPC which can supply a write signal to the head and take out a read signal from the head with high reliability in response to size reduction and thickness reduction of the disk drive.
In accordance with an aspect of the present invention, there is provided a disk drive comprising a housing; a disk rotatably mounted in the housing; a head for reading/writing data on the disk; an actuator arm rotatably mounted in the housing; a suspension having a base end portion fixed to a front end portion of the actuator arm and a front end portion for supporting the head, the suspension having a first conductor pattern connected at one end thereof to the head and a first terminal connected to another end of the first conductor; a main flexible printed circuit sheet fixed at one end portion thereof to the actuator arm, the main flexible printed circuit sheet having a second conductor pattern and a second terminal connected to one end of the second pattern; and an interconnection flexible printed circuit sheet mounted along a side surface of the actuator arm so as to extend substantially parallel to an upper surface of the actuator arm, the interconnection flexible printed circuit sheet having a third conductor pattern, a third terminal connected to one end of the third conductor pattern and the first terminal, and a fourth terminal connected to another end of the third conductor pattern and the second terminal.
Preferably, the side surface of the actuator arm has a projecting portion having a groove extending substantially parallel to the upper surface of the actuator arm, and the interconnection flexible printed circuit sheet is inserted in the groove of the projecting portion.
In accordance with another aspect of the present invention, there is provided a disk drive comprising a housing; a disk rotatably mounted in the housing; a head for reading/writing data on the disk; an actuator arm rotatably mounted in the housing; a suspension having a base end portion fixed to a front end portion of the actuator arm and a front end portion for supporting the head, the suspension having a first conductor pattern connected at one end thereof to the head and a first terminal connected to another end of the first conductor; and a flexible printed circuit sheet fixed at an intermediate portion thereof to the actuator arm, the flexible printed circuit sheet having a second conductor pattern and a second terminal connected to one end of the second conductor pattern and the first terminal; the flexible printed circuit sheet having a connecting portion formed between the intermediate portion and the suspension and mounted along a side surface of the actuator arm so as to extend substantially parallel to an upper surface of the actuator arm.
Since the interconnection flexible printed circuit sheet is mounted along the side surface of the actuator arm so as to extend substantially parallel to the upper surface of the actuator arm, the width of the interconnection flexible printed circuit sheet is not limited by the thickness of the actuator arm. Accordingly, an interconnection flexible printed circuit sheet having a relatively large width can be used, so that a required number of signal lines can be easily ensured and the pattern width of each signal line can be made enough large  large enough.
The above and other objects, features and advantages of the present invention and the manner of realizing them will become more apparent, and the invention itself will best be understood from a study of the following description and appended claims with reference to the attached drawings showing some preferred embodiments of the invention.